Field of the Invention
The invention generally relates to handling abnormal cases occurred during call setup, and more particularly, to apparatuses and methods for reducing call recovery time associated with the cell update procedure.
Description of the Related Art
With growing demand for ubiquitous computing and networking, various cellular technologies have been developed, including the Global System for Mobile communications (GSM) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for Global Evolution (EDGE) technology, Wideband Code Division Multiple Access (WCDMA) technology, High Speed Packet Access (HSPA) technology, Code Division Multiple Access 2000 (CDMA2000) technology, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) technology, Worldwide Interoperability for Microwave Access (WiMAX) technology, Long Term Evolution (LTE) technology, Time-Division LTE (TD-LTE) technology, and LTE-Advanced (LTE-A) technology, etc.
Take the WCDMA technology in compliance with the 3rd Generation Partnership Project (3GPP) Technical Specification (TS) 25.331 as an example. When detecting an abnormal situation (e.g., radio link failure) during a call establishment, a User Equipment (UE) should enter the CELL_FACH state from the CELL_DCH state, and perform the cell update procedure to recover the call. However, if the signal quality of the serving cell is bad, the cell update procedure may fail and the UE has to retry the cell update procedure until the maximum retry limit is reached. For example, in some WCDMA networks, the maximum retry limit may be set to 7 and the retry timer specifying the period of time between every two successive retries of the cell update procedure may be set to 8 seconds. As a result, the UE may spend at least 56 seconds in performing the cell update procedure for 7 times before it can release the signaling connection(s) and radio access bearer(s) to enter the RRC IDLE state in which it may reselect to a more suitable cell. That is, the user may experience an extremely long delay in obtaining services.